NAeA TN 2899 3
Tests were carried out at low altitude in the conditions shown in
the following table:
Landing Canopy
Condition Power setting Flaps
gear
Approach 21 in. Hg at 2,550 rpm Down Down Open
Glide Off Up Up Closed
Landing Off Down Down Open
Power-on clean 42.5 in. Hg at 2,550 rpm Up Up Closed
Wave-off 42.5 in. Hg at 2,550 rpm Down Down Open
Dive 15 in. Hg at 2,550 rpm Up Up Closed
Tests were also carried out at high altitude in the power-on clean,
glide, and dive conditions. The data were obtained by both the steady
and continuous record methods. In the steady method, the pilot either
dived or climbed the airplane to a given speed and, when the airplane
reached a steady condition, a record was taken of the re~uired values.
In the continuous method, the airplane was flown through the speed range
with gradually changing speed and the re~uired values were recorded
throughout the entire period. The data obtained by the continuous method
are indicated by flagged symbols. Standard NACA photographic recording
instruments were used to obtain the data. A description of this instru-
mentation is given in reference 2.
DISCUSSION AND RESULTS
LONGITUDINAL STABILITY AND CONTROL CHARACTERISTICS
Dynamic Longitudinal Stability
The short-period oscillation of normal acceleration and elevator
angle was investigated in the power-on clean, glide, and landing con-
ditions by abruptly deflecting and releasing the elevator at various
speeds throughout the speed range. Typical time histories of these
attempted oscillations are shown in figure 8. There was no oscillation
of the elevator, but the airplane diverged longitudinally, sometimes
violently, at low speeds in the power-on clean condition. (See fig. 8(a).)
This unstable condition is in all probability due to the static longi-
tudinal instability of the airplane.
NACA TN 2899 5
the slope became unstable above approximately 125 mph at the rearward
center-of-gravity position. The stick-fixed stability was neutral at
the rearward center-of-gravity position at speeds above approximately
130 mph. The requirement of reference 3 was not satisfied. It should
be noted that the flaps on the F-4TO-30 are of the blow-up type; that
is, the flap deflection varies with decreasing airspeed until a speed
is reached where the flaps remain full down. The variation of flap
deflection with airspeed is shown in figure 12.
Landing condition (fig. 13).- The requirement was satisfied as the
airplane was stable both with stick fixed and with stick free throughout
the permissible speed range at both the center-of-gravity positions
tested.
Wave : off condition (fig. 14).- The airplane was unstable with stick
fixed and with stick free in this condition and the requirement of refer-
ence 3 was not satisfied.
Neutral points (figs. 15 to 21).- The data shown in figures 15 to 20
illustrate the method used in obtaining the neutral points shown in fig-
ure 21. Since only two center-of-gravity positions were tested, the
actual numerical values of the neutral points may not be entirely accu-
r rate, but they do give a general picture of the stick-fixed and stick-
free S)ability . In the power-on clean condition, the stability parameter
d(Fe/q is always negative (see figs. 19 and 20); this fact indicates
deN
that the center-of-gravity position required to make the airplane stable
could not be obtained with any normal loading of the airplane. These
data also indicate that it would be useless to test the airplane at a
more rearward center-of-gravity position since it is already known that
the airplane will be unstable. The same condition existed in the wave-
off condition. In the approach condition a more accurate determination
of the neutral point was possible since data were obtained with the
center of gravity both forward and rearward of the neutral point. In
the glide and landing conditions the airplane was stable throughout the
speed range except at low normal-force coefficients in the glide condi-
tion where the stick-free neutral paints were slightly forward of the
rearmost center-of-gravity position tested. The neutral points would
have been better defined had a more rearward center-of-gravity position
been tested in these two conditions but the significance of these data
did not warrant the tests.
It can be seen from the above discussion that the application of
power had a definite destabilizing effect on both the stick-fixed and
stick-free stability. The adverse effect of rearward center-of-gravity
position is markedly shown and it should be noted that center-of-gravity
positions rearward of the rearmost test center-of-gravity position may
be obtained with normal loadings of the airplane.
12 NACA TN 2899
TABIE 1. - PERTINENT DIMENSIONS OF THE F-47D- 30 AIRPLANE
Engine . . . . . . . . . . . Pratt & Whitney R-2800-59
Propeller (four blades) Curtiss Dwg. No. SPA-5
Total wing area, SQ ft . . . . . . 300
Total aileron area, SQ ft . . ..... 25.7
Aileron-trim-tab area (left aileron), SQ ft 0.89
Stabilizer area, SQ ft . . . . . 33.0
Elevator area, SQ ft . . . . . . 22.0
Elevator-trim-tab area, sQ ft 0.94
Fin area, SQ ft . . . . . . . 13.9
Rudder area, SQ ft . . . . . . . . . 11. 9
Rudder-trim- tab area, SQ ft 0.87
~
NAeA TN 2899 l3
TABLE 11.- TRIM CHANGES OF F-47D-30 DUE TO FLAPS AND POWER
(a) Center of gravity, 0.291 mean aerodynamic chord,
gear retracted
Control force,
lb Change
Indicated in
airspeed, Power Flaps Gear
mph
sideslip angle,
Elevator deg
pull Rudder Aileron
164 50 percent Up Up 0 0 0 0
164 50 percent Up Down 5.4 1 left 0 .1 lef't
164 50 percent Down Down .8 9 left .6 right .5 right
166 Off Down Down 5.4 33 left 0 .2 right
139 50 percent Down Down 0 0 0 0
139 Off Down Down 3·9 62 left .6 right 2.7 right
162 Off Up Up 0 0 0 0
163 Off Up Down 3·9 1 left .6 left 0
165 Off Down Down 1.1 7 left 1.0 left 1.1 left
139 Off Down Down 0 0 0 0
138 Normal rated Down Down -8.5 9B right 0 2.2 left
139 Normal rated Down Down 0 2 right 0 2.5 left
13 8 Normal rated Down Up -3. 8 14 right .6 left 3.1 left
138 Normal rated Up Up -3·8 3 right .6 left 4.7 left
117 Normal rated Up Down 0 0 0 0
117 Normal rated Up Up -3. 8 19 right 0 .1 left
